Data transmission system

ABSTRACT

A terminal apparatus is described for a data transmission system which transmits messages constituted by a series of characters. The terminal apparatus includes means for checking the entering of messages for determining when errors occur in the manual entry of information. The terminal apparatus includes a manually operated means for entering characters, and a presettable means for indicating the position within the series of characters of a predetermined character which is to appear in a particular message format. A given message format may be selected from a number of message formats. A checking means is provided to determine if the predetermined character is entered in the proper position within a series of characters, and if not, an error signal is generated which indicates the absence of the predetermined character from the position in question.

United States Patent [72] Inventors Giovanni Zaffignani;

Bruno Brunialti, both of lvrea, Italy [21] App1.No. 838,608 [22] Filed July 2, 1969 [45] Patented Oct. 12, 1971 [73] Assignee Ing C. Olivetti & C.

S.p.A., lvrea, Italy [32] Priority July 2, 1968 33 Italy 3 1 1 52266-A/68 [54] DATA TRANSMXSSION SYSTEM 6 Claims, 4 Drawing Figs.

[52] US. Cl 235/153, 178/23 A, 340/146.1

51 1111.01 G06t 11 00 [50] Field of Search 340/1461,

[56] References Cited UNITED STATES PATENTS 2,673,236 3/1954 Phelps et al....... 178/23 X 3,267,427 8/1966 Hoek et al. 340/1461 2,958,727 l1/l960 Barbeauetal 178/23 FOREIGN PATENTS 968,279 9/1964 Great Britain 178/23 Primary ExaminerEugene G. Botz Assistant ExaminerCharles E. Atkinson AttarneyBirch, Swindler, McKie & Beckett ABSTRACT: A terminal apparatus is described for a data transmission system which transmits messages constituted by a series of characters. The terminal apparatus includes means for checking the entering of messages for determining when errors occur in the manual entry of information. The terminal apparatus includes a manually operated means for entering characters, and a presettable means for indicating the position within the series of characters of a predetermined character which is to appear in a particular message format. A given message format may be selected from a number of message formats. A checking means is provided to determine if the predetermined character is entered in the proper position within a series of characters, and if not, an error signal is generated which indicates the absence of the predetermined character from the position in question.

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CONCENTRATOR DATA PROCESSOR Fig.1

INVENTORS GIOVANNI ZAFF'IGNANI BRUNO BRUNIALTI DATA TRANSMISSION SYSTEM BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data transmission system with an error-checking device.

2. Description of the Prior Art In known systems; recourse is generally had to quite complex checking devices and error detection devices. In particular, some systems are concerned with the errors due to operating anomalies on the transmission line, and comprise complicated devices which verify the equality between the message at departure and the message at arrival or between single characters at departure and at arrival. Nevertheless, in the known systems normally the error due to the operator in the entering phase of the message on the peripheral input members is neglected. The system in accordance with the invention, on the other hand is provided with a device for checking the entering of the messages which is extremely simple and nevertheless having a high discriminative ability with regard to the errors which most commonly occur in the manual entering of the date.

SUMMARY OF THE INVENTION In accordance with the invention there is provided a data transmission system comprising a terminal apparatus provided with manually operable means for entering a message to be transmitted, the message being composed of a series of characters, presettable means for signalling the positions in the said series at which a predetermined character is to appear in a particular message format, and checking means adapted to check if the predetermined character is entered in the said positions and, if it does not, to operate error-signalling means. The invention will be described in more detail by way of example, with the aid of the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic representation of a data transmission system embodying the invention;

FIG. 2 is a block diagram of one terminal of the system;

FIG. 3 is a block diagram of a format checking device of the terminal; and

FIG. 4 is a diagram of a conversation procedure between a terminal and a concentrator of the system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to FIG. 1, an electronic data processor 2 is connected to a telecommunication system for centralized processing of the data which can be sent from various telegraphic terminals 3. These are connected to the processor 2 through concentrators 4, the terminals 3 being connected to the corresponding concentrators 4 by means of telegraphic channels 5 while the various concentrators 4 are connected to the processor 2 by means of telephonic channels 6.

The concentrators 4 can permit either the exchange of information between terminal and terminal or the exchange of information between terminal and the processor, which can operate either as collector of data or in real time. The following description concerns the conversation which can occur between terminal 3 and its concentrator 4, and more especially the case where the concentrator is placed at the disposal of the terminal which takes the initiative in the conversation, conversation which occurs by means of the procedure known as polling.

With the aim of detecting possible errors in the messages received from the terminal 3, the concentrator 4 is provided with known checking devices such as for example a redundancy-checking device, for checking the'total block of the code combinations of a message, and a check-digit" device adapted to check the numbers contained in a message, to each of which there has been added a parity bit. For the exchange of the information, the ISO code is used in the American version called RASCII (Revised American Standard Code for information Interchange) whose code combinations are of seven bits plus an eighth bit for the parity check of the combination.

Each terminal 3 comprises a teleprinter 7 (FIG. 2) placed under control of a line control unit 8 which regulates the conversation between the concentrator 4 and the teleprinter 7.

The teleprinter 7 comprises a transmission device 45 connected to the concentrator 4 by means of a telegraphic transmission line 9 and a reception device 10 connected to the concentrator 4 by means of a telegraphic reception line 11 and to the line 9 for the local recording of the code combinations transmitted. A keyboard 12 is used to enter the code to be transmitted on the line 9 and a device 13 prints the code combinations received on a writing support such as a sheet of paper or continuous forms.

Each key of the keyboard 12 is adapted to operate simultaneously and selectively a series of eight code bars 14 under the control of a mechanism 15 having a cyclic operation, for example as described in our US. Pat. No. 3,306,4l7. Each code bar of the group 14 with the exception of the bar associated with the parity bit of the code is also arranged to actuate a corresponding electrical contact, the group of seven indicated contacts being generally by 16 in FIG. 2. The group of contacts 16 is used for the format check as is better described further on.

The printing device 13 is connected to the receiving device 10 by way of a parity check device 17 and a function recognition device on discriminator 18. The device I7 is adapted to execute a cross check of the eight bits of each code combination received and to send by means of an output line 18' a signal to the control unit 8 whenever it detects an error. The device 18 is adapted to discriminate the code combinations received which have to be written by the printing device 13 from the code combinations characteristic of the conversation procedure with the concentrator 4 (FIG. I), which require a reply from the terminal 3 in accordance with the procedure itself. To that end, the device I8 is provided an output with a series of nlines 19 connected to the control unit 8, each of which is associated with a specific code combination characteristic of the procedure and on which there is sent a signal whenever the device 18 recognizes the corresponding combination.

The line control unit 8 is connected by means of a series of mlines 20 to a group of melectromagnets 21, each of which is arranged to command on the keyboard 12 the key which corresponds to the code combination to be transmitted in accordance with the conversation procedure with the concentrator. The line governor 8 is, moreover, connected by means of another series of klines 22 to a group of kelectromagnets 23 arranged to block totally or selectively the keys of the keyboard 12.

The terminal 3 is provided, moreover, with a formatchecking device 24 which is used to verify the correct making up of the message on the part of the operator. The formats are of various types according to the work schedule which the operator has to execute. Each format in which it is necessary to make up the message has a predetermined structure and will be called hereinunder a program."

Provided for within the framework of a program" are various subformats, called subprograms," which, for example, let us suppose may be at the most seven for each program. The subprograms can comprise parts having a predetermined structure to be compiled in a binding manner by the operator and which require an error check on the part of the device 24 and parts having a nonpredetermined structure and which are compiled in a nonbinding manner which does not require an error check on the part of the device 24. Hereinunder we will call the aforesaid parts having a predetermined structure and the aforesaid parts having a nonpredetermined structure, the fixed modules" and the variable modules" respectively.

The format check is effected only when the terminal uses the polling procedure or operates locally. The message is checked by means of the character SPACE and/or NL (new line) which is constituted by the sequence of code combinations RT-DEL-INT (return carriage and line feed). It is supposed for example that the number of advances step by step which the carriage of the printing device can effect from start to finish of a line is 80 To operate within the framework of a program, the keyboard 12 of the teleprinter comprises a group of eight keys 26 each associated with a specific writing sign [for example namely equals, stroke, colon, open brackets, comma, apostrophe, close brackets, stop seven of them to select a subprogram and the eighth (stop) to exclude the format check.

The format'checking device 24 comprises a decoding cir' cuit 27 (FIG. 3) adapted to recognize the operation on the keyboard 12 of one of the seven subprogram keys and of the forrnat-check-exclusion key. To that end, the circuit 27 is connected at its input to the seven contacts 16 and is provided at its output with eight wires 28, on each of which there can appear a logical l according to the subprogram key or the format-check-exclusion key depressed. Each of the eight wires 28 is then connected to cell constituted by a flip-flop of a register 29 arranged to memorize the choice of the subprogram or of the format-check exclusion. The setting of each of the flip-flops of the register 29 in accordance with the logical l on any one of the eight wires 28 is placed under the time control of a signal which appears on a line 30 whenever an electrical contact 31 is closed in each cycle of the mechanism 15 (FIG. 2). The register 29 is so constituted that, when any flipflop associated with a subprogram is set, it prohibits the other six from being set but leaves free the flip-flop relative to the format-check exclusion which can thus be set even during the typing of the message in accordance with the subprogram selected.

The register 29 is provided at its output with eight wires 32 connected to a logical interface circuit 33 adapted to notify to the line control unit 8 the selection which has occurred of a subprogram or of the format-check exclusion. The line control unit 8 in such a case, by means of circuits not shown in the drawings but known in themselves, commands by way of one of the lines 22 in the unblocking of the group of eight keys 26.

The format-checking device 24 comprises, moreover, a counter 34 arranged to count the cycles of the mechanism 15 following selection of a subprogram. To this end, the contact 31 is connected by means of a line 35 to the input of a gate circuit 36 which permits the output on a line 37 connected to the counter 34 of an impulse to be counted only if the circuit 36 is enabled by way of another line 38 from the register 29, an enabling signal being present on the line 38 whenever any one of the seven flip-flops associated with a subprogram is set.

Since the number of step-by-step advances which the carriage of the printing device 13 (FIG. 2) can carry out from start to finish of a line is 80, the counter 34 (FIG. 3)can be realized for example by means of two ring counters, each comprising nine flip-flops.

Initially the first register is in an initial position, which we will call the reset position, in which a single flip-flop is at logical level 1." This shifts from one flip-flop to the other of the first register at each signal on the line 37 and at each ninth one of these signals goes back to the initial flip-flop (RESET). Every time that it passes through this initial position there is shifted a logical level 1 from one flip-flop to the other of the second register. The maximum capacity of the counter 34 is 9-9=8 l. The counter 34 is connected to a logical circuit 39 arranged to reset the counter 34 itself by way of a line 40 and simultaneously to reset the register 29 by way of another line 41. The logical circuit 39 responds to reset the counter 34 and the register 29 either to a signal on a line 42 connected to an electrical contact 43 which is closed whenever the key INT (line feed) is operated, or a signal from the line control unit 8 through connections 44 on which there can be sent signals in relation to the exchange of specific code combinations (example ACK) provided for in the conversation procedure between terminal and concentrator. The logical circuit 39 can finally be arranged to reset the counter 34 and the register 29 in any known manner immediately upon the manual operation of a lRESET key provided on the keyboard 12 but not shown in the drawings.

The contact 43 is also connected by means of a line to the line control unit 8. When a signal is present on the line 80 consequent on the closure of the contact 43, it brings about through the connection 22 the total blocking of the keyboard 12.

The counter 34 is connected to a matrix of diodes 46 for decoding the signals on nine output wires 47 from the first register and on nine output wires 48 from the second register.

Each node of the matrix ANDs the signals on the two wires which correspond in the groups of nine wires 47 and 48 is connected by means of a wire 49 to an electrical contact 1 to 80 of a program connector 51, with the exception of the first node of the matrix 46 corresponding to the RESET position of the counter which is not used.

The program connector 51 is provided at its output with seven contacts 1' to 7 each associated with a subprogram. Each contact 1 to 7 is connected with one or more of the contacts 1 to 80 corresponding to the positions in the format to be checked which are the positions in which there is provided a SPACE character. Moreover, all the contacts 1' to 7' are connected to the contact 80 since this corresponds to the final position of end of line in the format in which there is provided the entering of a character NL. The connector 51 is interchangeable with other connectors prewired in accordance with various format programs.

Each of the seven contacts 1 to 7' is connected by means of a wire 52 to a circuit 53 constituted by seven gates, each of which permits the output of a signal on a single line 54 only if the gate itself is enabled by way of another input line 56 connected to a subprogram cell of the register 29. On each line 56 there is present an enabling signal for the corresponding gate whenever the relative subprogram is selected.

The line 54 constitutes one input to an exclusive OR gate 57 which has another input line 58 on which there is present a signal whenever the key SPACE or NL RC-DEL-TNT) is operated on the keyboard. Thus the line 58 constitutes the output of a staticizing circuit 59 for the code RC or SPACE. The circuit 59 is constituted by a flip-flop which is conditioned to set by a signal on a line 61 which is energized upon the closure of the one or the other of two contacts 62 or 63 respectively associated with the entering of the code SPACE or RC. The flip-flop, when so conditioned, is set and, immediately after, reset by two Successive signals on the line 30, the first of them corresponding to the operation of the key SPACE or RC and the second of them corresponding to the successive operation of any key whatever.

The exclusive OR circuit 57 has an output line 62 on which there is obtained an error signal when on the two inputs 54 and 58 there is present only one of the two signals. The line 30 is also connected to the circuit 57 so as to enable the output of an error signal only in synchronism with the closure of the contact 31.

The line 62 is connected by way of a logical interface circuit 63 to the line control unit 8 to signal the error. The line control unit 8 in such a case, by means of circuits not shown in the drawings, but known in themselves, is arranged to command by way of one of the lines 21 the entering into the keyboard of the code sequence NL (error sequence) and by means of one of the lines 22 the total blocking of the keyboard 12. This total blocking of the keyboard by means of appropriate circuits of the line control unit 8 is maintained only for a predetermined interval of time, after which the group of subprogram keys 26 alone is freed.

The program connector 51 is also provided with another seven output contacts 1e to 7e for the programmed exclusion of the format check. Each contact he to 7e is connected with one or more of the contacts 1 to 80 correspondingly to the format positions in which one passes from a fixed module" to a variable module. Each of the seven contacts 1e to 7e is connected by means of a wire 66 to a circuit of seven gates 67 the same as the circuit 53. Each gate of the circuit 67 is enabled to send a signal on a single output line 68 if a signal is present on the corresponding line 56, as for the circuit 53.

The line 68, by way of a logical interface circuit 69, is arranged to signal to the line control unit 8 the exclusion of the format check. The line control unit 8 in that case ignores the error signals which may be by the circuit 63 and, by means of circuits not shown and known in themselves, and by way of the connection 22 (FIG. 2) keeps the keyboard 12 totally unblocked until the entering of the end of message sequency NL. The format-checking exclusion can also be obtained by entering the code (stop) on the group of keys 26. To that end, the flip-flop of the register 29 corresponding to this code is connected by means of a line 71 to the interface circuit 69. A signal on the line 71 corresponding to the manual selection on keys 26 of the format check exclusion has the same effect as a signal on the line 68. The format check exclusion can also be obtained freely by means of the sending of a signal on another line 72 in any known manner.

The conversation from terminal to concentrator occurs in the following manner. Initially with the teleprinter 7 (FIG. 2) fed and started the keyboard 12 is completely blocked with the exception of the EOT key. The operator initiates the conversation (see also alfo FIG. 4) by sending to the concentrator 4 (FIG. 1) the code combination EOT. The reply from the concentrator 4 to the teleprinter 7 (FIG. 2) will be be ACK, received by the functions group 18 and signalled to the line control unit 8 by way of the connection 19. The line control unit 8 then commands:

a. the RESET of the counter 34 (FIG. 3) of the formatchecking device by way of the connection 44;

b. the unblocking of the group 26 of the Subprogram characters of the keyboard 12 by means of the connection 22.

The operator can then select a key of the group 26 in accordance with the subprogram to be compiled. This selection involves signalling via the circuits 16, 27, 29 and the interface circuit 33 to the line control unit 8 which then commands the total unblocking of the keyboard 12 by means of the connection 22. The operator then composes the message which ends with the entering of the code sequence NL (RC-DEL-INT. The code RC through the closure of the contact 63, the circuit 59 and the line 58 sends a signal to the exclusive OR circuit 57 which serves to check the correctness of the part of message composed; the code INT. produces instead:

a. the RESET of the counter 34 for the printed characters by means of the closure of the contact 43 and by way of the circuit 39;

b. the reestablishment of the total blocking of the keyboard 12 by way of the line control unit 8 because of the sending of a signal on the line 80 consequent to the closure of the contact 43.

In the case of a positive reply of the concentrator ACK there will again be repeated the preceding operations; thus the operator will be able to select a second subprogram or send to the concentrator the end of transmission code ETX. In this second case, the calculator will reply EOT which is received by the functions group 18 and by way of the connection 19, the line control unit 8 and the connection 20, causes the teleprinter 7 to send ACK which will be recognized also by the functions group 18 which, by way of the line control unit 8 will bring the terminal back into the initial conditions.

During the polling procedure, if the concentrator 4 detects an error, it sends a message (see H6. 4) of reply which commences with STX and ends with NL at the point at which the error has been detected and concludes with ETB. This message is checked by the parity-checking device 17 of the terminal which by way of the line governor 8 and the connections 20 will reply ACK in the case that the reception is correct or NACK in the case of an error on the parity check. In the first case (emission of ACK) the line control unit 8 by means of the connection 22 brings the terminal back into the initial conditions, in the second case (emission of NACK) the keyboard will continue to be blocked and the connector will repeat the message until it is correctly received.

During the compilation of a subprogram, if the operator depresses in place of the SPACE another character, thanks to the circuits 57, 63 and the connections 20, 22 and 41 there are the following conditions:

a. total blocking of the keyboard for a predetermined interval of time (for example 1 sec.);

b. generation of the sequence NL;

c. reset of the counter;

d. unblocking on the keyboard of the zone of the subprogram keys after the said interval of total blocking.

It will be understood that the connections in the connector 51 are effected in such manner as to avoid the establishment of sneak paths to the terminals 1' to 7e What we claim is:

1. Terminal apparatus for a data transmission system which transmits messages constituted by a series of characters at least between a terminal and a central processor, comprising:

manually operable means for entering said characters into said terminal apparatus,

presettable means for defining message formats including means for generating a signal indicative of the position in said series of characters at which predetermined characters are to appear in each said message format,

selecting means for selecting a predetermined one of said message formats,

checking means jointly controlled by said presettable means and said selecting means for checking whether each one of said predetermined characters has been entered in said positions, and

error-signalling means controlled by said checking means for generating a signal indicative of the absence of a predetermined character from at least one of said positions.

2. Terminal apparatus according to claim 1, wherein the presettable means comprises a counter arranged to be reset in response to a signal indicative of a second predetermined character and then to count the number of characters entered,

means settable to respond to predetermined states of the counter to provide a first signal, the checking means being arranged to provide a second signal whenever the first predetermined character is entered by the manually operable means and to check for coincidence between the first and second signals.

3. Terminal apparatus according to claim 2 wherein said selecting means comprises a plurality of manually operable members each one operable for selecting a corresponding format, each one of said members when operated causing said checking means to be controlled by said settable means according to the associated group of positions, said settable means comprising:

a series of first terminals which are energized in turn as the counter counts through its states, different groups of said first terminals being connected by interchangeable connections to each of a series of second terminals which correspond to the different formats, respectively, and means for connecting that one of said second terminals to the checking means which corresponds to the selected manually operable member.

4. Terminal apparatus according to claim 3 wherein operation of a manually operable member operates a means for causing the apparatus also to transmit a code identifying the selected format.

5. Terminal apparatus according to claim 3 further comprising a remote apparatus in communication with said terminal apparatus, the latter apparatus comprising a keyboard including a group of keys which constitute the said manually operable members and means for selectively blocking keys, and a control unit responsive to a first code from the remote apparatus to operate the blocking means to block all keys other than the said group and further responsive to operation of one of the said group of keys to operate the blocking means to unblock all keys.

keys for a predetermined interval of time and then to unblock only the said group of keys. 

1. Terminal apparatus for a data transmission system which transmits messages constituted by a series of characters at least between a terminal and a central processor, comprising: manually operable means for entering said characters into said terminal apparatus, presettable means for defining message formats including means for generating a signal indicative of the position in said series of characters at which predetermined characters are to appear in each said message format, selecting means for selecting a predetermined one of said message formats, checking means jointly controlled by Said presettable means and said selecting means for checking whether each one of said predetermined characters has been entered in said positions, and error-signalling means controlled by said checking means for generating a signal indicative of the absence of a predetermined character from at least one of said positions.
 2. Terminal apparatus according to claim 1, wherein the presettable means comprises a counter arranged to be reset in response to a signal indicative of a second predetermined character and then to count the number of characters entered, means settable to respond to predetermined states of the counter to provide a first signal, the checking means being arranged to provide a second signal whenever the first predetermined character is entered by the manually operable means and to check for coincidence between the first and second signals.
 3. Terminal apparatus according to claim 2 wherein said selecting means comprises a plurality of manually operable members each one operable for selecting a corresponding format, each one of said members when operated causing said checking means to be controlled by said settable means according to the associated group of positions, said settable means comprising: a series of first terminals which are energized in turn as the counter counts through its states, different groups of said first terminals being connected by interchangeable connections to each of a series of second terminals which correspond to the different formats, respectively, and means for connecting that one of said second terminals to the checking means which corresponds to the selected manually operable member.
 4. Terminal apparatus according to claim 3 wherein operation of a manually operable member operates a means for causing the apparatus also to transmit a code identifying the selected format.
 5. Terminal apparatus according to claim 3 further comprising a remote apparatus in communication with said terminal apparatus, the latter apparatus comprising a keyboard including a group of keys which constitute the said manually operable members and means for selectively blocking keys, and a control unit responsive to a first code from the remote apparatus to operate the blocking means to block all keys other than the said group and further responsive to operation of one of the said group of keys to operate the blocking means to unblock all keys.
 6. Terminal apparatus according to claim 5, wherein the control unit is further responsive to an error signal from the checking means to operate the blocking means to block all keys for a predetermined interval of time and then to unblock only the said group of keys. 